The CDC has an important message for parents: Your kids might be using too much toothpaste, and it can actually be dangerous for their oral health.

Kids between the ages of three and six aren't supposed to use more than a pea-sized amount, per the American Dental Association (ADA). Kids under three should only use a smear the size of a grain of rice.

But according to a new CDC report, plenty of children are using way more than that.

For the new study, researchers analyzed nationally representative survey data from parents with kids between the ages of 3 and 15 that was collected between 2013 and 2016. In all, data for 5,157 kids were included in the study.

The results showed that nearly 40 percent of children between three and six are using more toothpaste than dentists recommend. In fact, about 60 percent of kids between ages 3 and 15 used a half or full toothbrush load of toothpaste when they brushed. In the 3-to-6-year-old age group, 12 percent used a smear, 49.2 percent used the correct pea-sized amount, 20.6 percent used half a toothbrush load, and 17.8 percent used a full toothbrush load of toothpaste.

"The findings suggest that children and adolescents are engaging in appropriate daily preventive dental health practices," the authors wrote. "However, implementation of recommendations is not optimal."

Toothpaste seems pretty harmless, but using too much can cause problems.

The big concern here is fluoride, the researchers said. Fluoride is a mineral that’s important for reducing tooth decay when it’s used appropriately, according to the ADA. It’s often found in toothpaste and in many public water systems.

Although fluoride is generally considered a good thing for teeth (and the ADA recommends that you brush your child’s teeth with a fluoride toothpaste), brushing with too much fluoride toothpaste can actually damage a child’s tooth enamel (the hard, outer surface of their teeth) when they swallow it, the CDC says. And younger kids inevitably do swallow the toothpaste they brush with, Danelle Fisher, M.D., vice chair of pediatrics at Providence Saint John’s Health Center in Santa Monica, California, tells SELF. “Kids under the age of six don’t spit very well,” she explains.

Too much fluoride can also cause discoloration and pitting, a condition known as dental fluorosis, the CDC says. If fluoride discolors a child’s teeth, it can make them appear mottled, lacy white, or, in severe cases, brownish, Mia L. Geisinger, D.D.S., M.S., associate professor in the University of Alabama at Birmingham School of Dentistry’s Department of Periodontology, tells SELF. And the potential issues aren’t just limited to teeth: Too much fluoride can even affect a child’s bone density, Dr. Fisher says. “This is actually a really serious thing,” she adds.

It's recommended that adults also stick with pea-sized amount, but this isn’t as much of an issue for grown-ups. “It's not as concerning for adults because their teeth and bones are developed,” Jamie Alan, Ph.D., Pharm.D., an assistant professor of pharmacology and toxicology at Michigan State University, tells SELF. You can still technically consume too much fluoride and potentially have issues with your bone density as a result, but if you're brushing properly and spitting out your toothpaste adequately like most adults do, toothpaste shouldn't cause any adverse effects, Alan says.

This really only becomes an issue if your child consistently goes overboard on the toothpaste long-term.

Sure, at some point your kid probably used too much toothpaste, and that’s okay; using too much fluoride toothpaste every once in a while is probably fine. But it's an important thing to keep an eye on: “This is not about using too much toothpaste once or twice,” Mark S. Wolff, D.D.S., Ph.D., dean at the University of Pennsylvania School of Dental Medicine, tells SELF. “It’s for years.” Basically, you'll want to correct your child's habit sooner rather than later.

While too much fluoride use is a potential issue, Dr. Geisinger says you don't need to worry too much. Just monitor your child’s toothpaste usage, watch them brush to make sure they're doing it well, and keep the tube out of their reach when they’re not using it.